Harmonic suppressor



Jul 8-; 1924. 1,500,555

L. ESPENSCHIED mmmomc SUPPRESSOR Filed Sept. 27, 1919 Patented July 8,1924.

EEG

LLOYD ESPENSCHIED, 0F HOLLIS, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

HARMONIC SUPPRESSOR.

Application filed September To all whom it may concern.

Be it known that I, LLOYD EsPnNsoHIEn, residing at Hollis, in the countyof Queens and State of New York, have invented certain Improvements inHarmonic Suppressors, of which the following is a specification. I p

This invention relates to transmission systems and more particularly tosystems arranged for the multiplex transmission ofa plurality of carriercurrents.

'The development of the art of multiplex transmission wherein a numberof carrier channels of communication are superimposed upon the sametransmission medium is tending to greatly increase the require ment ofthe carrier current in respect to its purity of wave form, or in otherwords, its freedom from harmonics. V This is because the presence ofharmonics in asystem of superimposed carrier channels tends to causeinterference as between the channels of lower frequency and those offrequencies representing harmonic multiples thereof.

Accordingly it is a general purpose of this invention to provide meanswhereby harmonics may be suppressed in both radio and wire carriercurrent transmission systems, and whereby the wave form of the carriercurrents transmitted out over the line may be purified. Other andfurther features and purposes of the invention will appear more fullyfrom the detailed description herein-' after given.

In systems of radio transmission there is available but a singletransmission medium and accordingly it is especially important in orderto obtain a maximum number of communications in a given frequency zonethat the carrier wave employed be of as pure form and as free fromharmonics as possible. Certain types of continuous wave generatorsutilized at present at transmitting stations of a radio system have apronounced tendency to produce harmonics of the original or fundamentalwave. For purposes of il-. lustration it is pointed out that the type ofgenerator or converter employing the well known Poulsen arc is of thetype in which harmonics are especially prominent. It has heretofore beenthe. practice to employ the arc generator in combination with a localtuned circuit loosely coupled with the an-.

tenna circuit. The type of coupling hereto- 27, 1919. Serial No.326,737.

the local tuned circuit with the antenna would be to couple the twocircuits through a low pass filter, which by being designed to readilytransmit the desired frequencies and to attenuate and practicallyextinguish frequencies above such range, would serve to shut outharmonics.

A further feature of the invention con sists in providing a means forthe elimination of harmonics in a multiplex transmission systememploying wire lines as the medium upon which the carrier currents aresuper imposed. A specific illustration wherein the presence of harmonicswould be detrimental to the transmission eificiency of the system wouldbe in the case where a low frequency channel for purposes of signalingwas super imposed on a line over which currents for telephonic purposeswere being transmitted, as the harmonics of the signaling currents mightbe within the telephonic range of frequencies. By utilizing a loosecapacity type of coupling between the tuned circuits in the branch fromwhich the low frequency signaling currents is transmitted to the line ameans is provided by this invention for eliminating harmonics whichwould other- Wise tend to be transmitted over the teleand 9 of the wellknown Poulsen arc type of generator. The local circuit 10 is looselycoupled to the antenna clrcuit 1 by means of the capacity 5. Thearrangement may be designed so that with respect to certain frequencies,the oscillations generated in circuit 10 may readily be transmitted tocircuit 41 and thence propagated in the ether by antenna 1. However theeffectiveness or transmission efficiency of the coupling includingcapacity 5 between circuits 10 and 4: decreases or diminishes as'thefrequency of the oscillations increases. Accordingly, while frequenciesof the fundamental or desired value may readily be transmitted fromcircuit 10 through the capacity. coupling to circuit 4, the higherfrequencies, such as the harmonicsgenerated, will not be readilytransmitted through the coupling but will be eliminated.

In the Fig. 2 is illustrated a modifica tion of the arrangementsillustrated in Fig. 1. Similar reference numerals have been used todenote like parts in both figures. The arrangement illustrated in Fig. 2is the same as that illustrated in Fig. 1 except that the localtuned'circuit 10 is coupled a Wire line L as a medium. As line L may beutilized for the multiplex transmission of currents for differentpurposes there is associated with line L the telegraph circuits 15 and17, and the telephone circuits 19 and 21. Included in the telegraphcircuits 15 and 17 are the composite sets 16 and 18 adapted to readilytransmit currents suitable for telegraphic purposes but which shut outcurrents suitable for other purposes and thereby prevents such currentsfrom interfering with the telegraph appa ratus. Included in thetelephone circuits'19 and 21 are he filtering devices 20 and 22 ing afrequency in the-neighborhood of 133 r The circuits 2 1 and 25 aretuned,

cycles.

by suitable arrangements of inductance and capacity to be resonant tocurrents of a frequency suitable for signahng such as 133 cyclecurrents, and accordingly readily allow the transmission of suchcurrents but serve to attenuate and extinguish other frequencies.

currents Associated with the incoming end of line L is the circuit 27which is tuned by means of a suitable arrangement of inductance. andcapacity to be resonant to current of frequencles sultable-for signalingpurposes such as 133 cycle currents, thereby readily allowingthetransmission of such currents but which serves to attenuate and shut outcurrents of other frequencies. The circuit 27 is coupled loosely throughthe capacity type of coupling 27 to the input circuit of anamplifier-rectifier 28, which may be of any desirable type.

The output circuit of the amplifier-rectifier to the antenna circuit 1by means of a filter device 14. This filter, which is commonly 28includes the direct current relay 29 which in turn may control anydesirable type of local signaling circuit, such as circuit 30. Thecapacity type of coupling, such as couplings 26 and 27 may be .designedto readily transmit currents of a frequency suitable for signaling. Ashas already been pointed out the effectiveness of this type of couplingdiminishes as the frequency increases andaccordingly serves tointerpose.

a greater transmission loss for the harmonic frequencies thanfor theoriginal or fundamental frequencies. With such an arrangement any of theharmonic frequencies-produced by the generator 23 and whiclrbeing withinthe telephonic range, would tend to interfere with the telephonecircuits associated with line L, will be suppressed and in terferencebetween the signaling and Male 3 phonic currents will be diminished.

lVhile the invention has been disclosed as embodied in certain specificarrangements which are deemed desirable it is understood that it iscapable of em odiment in many and widely varied forms Without departingI;

from the Sp r t of the invention asdefined in the appended claim.

WVhat'is claimed is; p telephone line arranged for the multiplextransmission of telephonic currents capacity coupling between saidselective circuit and said second circuit.

In testimony whereof, I, have signed my 10 name to this specificationthis 25th day of September 1919.

LLOYD ESPENSGHIED.

